This will apply to all divs though -- if you prefer you can add the overflow: hidden; property to all of the div ids in your above code instead of applying the overflow property to every div. Up to you.

Alternatively, put all of the HTML code for this montage inside a container div (called imagecontainer in the code below), and then you could just do:

#imagecontainer div {
overflow: hidden;
}

That's a quicker way to apply the property to all the divs in the container without affecting all divs on the page.
Hope this helps